Tubular fabrics intended for use in medical applications often have complex shapes and are usually cut by hand. A conventional technique for cutting fabric for use in medical applications includes manually heat-cutting the fabric with a soldering iron-type tool. Manual heat-cutting often results in an uneven edge and loose fibers extending from the cut line. In some processes, such heat-cutting is followed by manually trimming the cut edge with scissors under a microscope in attempt to correct uneven areas and decrease the number of loose fibers. However, because the second, trimming step is also a manual step, unevenly cut fibers from the original heat cut and/or the scissors cut can remain along the cut edge, creating a risk for fraying. Another disadvantage of such a manual cutting process is that the second cut with scissors represents “re-work” designed to correct imprecision in the first cut. Thus, a second, labor-intensive cutting step increases the cost of the manufacturing process.
In tubular fabrics, for example, fabrics for use as an endovascular graft, the fabric is manually rotated to cut the fabric around the circumference of the tube. A disadvantage of manually rotating and cutting the tubular fabric is that moving the fabric from one position to another can further cause imprecise or even cuts. In addition, manual cutting can lead to variability in quality of cuts between different operators.
After the fabric is cut twice—first by a soldering iron-type tool and then by trimming with scissors—the fabric edge can be placed under a microscope and “lightly” heat sealed so as not to further disturb the trimmed edge. However, a disadvantage of “light” heat sealing is that routine handling of the fabric can disrupt the “light” seal, thereby allowing cut yarn ends to become loose and possibly cause the fabric to fray and/or unravel.
Some tubular fabrics can have two or more adjacent tubular limbs, for example, an endovascular graft that has bifurcated limbs for placement into two smaller arteries branching from a larger artery. Such adjacent-limbed tubular fabrics create another cutting challenge. A tubular fabric having two adjacent limbs can be mounted on a mandrel for rotating while a cut is being made about the circumference of the limbs. However, when the tubular fabric is rotated, a cutting tool cannot reach the “inside” portions of the limbs that are facing each other. In some conventional cutting techniques, the legs of the mandrel are loosened from the mandrel body, rotated, and re-tightened so as to expose the uncut portions for cutting. This movement of the mandrel legs can cause movement of the fabric about the limbs. As a result, such movement in conventional cutting techniques can cause unevenness between the two partial cuts on each limb, and undesirably allows one limb to be cut a different length than the other limb.
The tolerance for cuts of fabrics used in many medical devices is narrow, for example, less than about 0.5 mm from the intended line of cut. Therefore, quality control variances in manually rotated and cut fabrics and in fabrics having adjacent tubes that are partially cut, repositioned, and finish cut are often unacceptable in fabrics designed for use in medical applications, particularly in implantable medical devices.
Thus, there is a need to provide a fabric cutting system and method that provide reliably precise cuts. There is also a need for such a fabric cutting system and method that meet quality control requirements for tubular fabrics used in medical applications. There is also a need for such a fabric cutting system and method that provides a completely sealed edge at a cut location. There is also a need for such a fabric cutting system and method that are efficient and cost-effective.